Mobile Unit Wattage

[WRUA262]

18 hours ago, wayoverthere said:

Trying another cable would help reduce the possibility of a bad cable being the issue.  One other thought that hit me was taking a multimeter to that power supply, just to make sure it's putting out what it should be, both current and voltage. 30a (even peak rated) should be more than enough for 25 watts (the vertex and btech show 10-11amps draw on high power), and i'd expect around 5amps for a 25 watt radio.

if both of those check out, i'm leaning toward the radio is the issue.

Checked the power supply. Operating at 13.5 volts, not sure how to check the current on my cheap multimeter, so I'll assume it's doing what it should be doing. Threw on a few ferrite collars on the LMR400 cable next to the antenna feed, adjusted the antenna slightly and was able to get about 14.5 watts out of the unit, and brought the SWR down to 1:17. Minor improvements. Wondering if more ferrite collars would help more. Have 3 on now, 2 more available. How many ferrite collars are too many?

[wayoverthere]

1 hour ago, WRUA262 said:

Checked the power supply. Operating at 13.5 volts, not sure how to check the current on my cheap multimeter, so I'll assume it's doing what it should be doing. Threw on a few ferrite collars on the LMR400 cable next to the antenna feed, adjusted the antenna slightly and was able to get about 14.5 watts out of the unit, and brought the SWR down to 1:17. Minor improvements. Wondering if more ferrite collars would help more. Have 3 on now, 2 more available. How many ferrite collars are too many?

It would need to be inline with one of the leads and set to amperage, if it has that option. Voltage holding is a good sign though.

Afaik, more ferrites won't hurt anything, and i might double check if theres anything close and metal near the antenna that might be affecting swr.

[WRUA262]

12 hours ago, wayoverthere said:

It would need to be inline with one of the leads and set to amperage, if it has that option. Voltage holding is a good sign though.

Afaik, more ferrites won't hurt anything, and i might double check if theres anything close and metal near the antenna that might be affecting swr.

Nothing of metal that would effect the SWR, the antenna is mounted in my attic. Wood frame. foam insulation, asphalt roof tiles. I can live with 1.17 - 1.20. 

I'll throw on the last 2 ferrites and see what happens. I wouldn't think that I'd be losing that many watts from a 35' LMR400 cable, but who knows? It's reading a full 5 watts on the lower power frequencies.

[gortex2]

The only true test is a dummy load on your meter and verify you see high power into the dummy load. If its 25 +/- 10% then you can dig into antenna system but without a true known level its hard to know if its the radio or the meter.

[PRadio]

1 hour ago, gortex2 said:

The only true test is a dummy load on your meter and verify you see high power into the dummy load. If its 25 +/- 10% then you can dig into antenna system but without a true known level its hard to know if its the radio or the meter.

I was getting on to say the same thing. It says so right in the user's manual. I have the same meter. 

 

surecom_sw_102_users_manual.pdf

[WRUA262]

On 2/2/2023 at 12:31 PM, PRadio said:

I was getting on to say the same thing. It says so right in the user's manual. I have the same meter. 

 

surecom_sw_102_users_manual.pdf 410.45 kB · 0 downloads

Good info, didn't see that before on the SWR meter manual.

Came across a Gadget Talk review from a year ago, he put the DB25G on a dummy load at high power and it only came through at max ~15 watts. I feel a little better after watching that review.

But then again, Notarubicon measured his unit... let me rephrase... ran the DB25G on a dummy load and it came through at just under 25 watts. Hmmmm. I guess I'll just have to spend the $$ on a 50W dummy load so I'll be able to sleep at night again.

[Sshannon]

2 hours ago, gortex2 said:

The only true test is a dummy load on your meter and verify you see high power into the dummy load. If its 25 +/- 10% then you can dig into antenna system but without a true known level its hard to know if its the radio or the meter.

A good bidirectional watt meter can be very helpful for this purpose with the actual antenna connected. 

[KAF6045]

1 hour ago, WRUA262 said:

But then again, Notarubicon measured his unit... let me rephrase... ran the DB25G on a dummy load and it came through at just under 20 watts. Hmmmm. I guess I'll just have to spend the $$ on a 50W dummy load so I'll be able to sleep at night again.

Check the derating curve for that dummy load. I have a 300W dry dummy load -- the derating curve gives it 4.5 minutes at 25W before needing a long cool-down. (It's only 1.5 minutes at 100W!)

I have the DB20-G -- advertised as 20W but the manual states 18W for GMRS. A 15W Midland MXT115 actually reads almost a watt higher than the 13W I get on repeater (467MHz) channels. It does exceed 20W on 2m VHF, and is a bit stronger (13.5W?) on GMRS simplex (462MHz). NOTE: this is the second DB20-G; I returned the first one for the same low power output, but the replacement showed the same.

[wayoverthere]

I would take the reviewer's results with a grain of salt.

Nothing against them (and call me jaded if you want), but I also wouldn't put it past the companies making sure the units going out to be reviewed are "healthy" examples, compared to what gets shipped to the average buyer.

[WRUA262]

As a follow-up - Bought a 50W dummy load, ran the radio again through the dummy load - ~15 watts, same as when I ran it through the antenna.

Next course of action is to get hold of Radioddity and see what they say. I get that the watts may be a little under stated, but 10-12 watts under is a far cry from 'a little' IMO.

[Sshannon]

14 minutes ago, WRUA262 said:

As a follow-up - Bought a 50W dummy load, ran the radio again through the dummy load - ~15 watts, same as when I ran it through the antenna.

Next course of action is to get hold of Radioddity and see what they say. I get that the watts may be a little under stated, but 10-12 watts under is a far cry from 'a little' IMO.

It’s important to note that there have been a lot of Surecom SW-102 meters reported within this forum that have really lousy accuracy.  How can you be sure it’s not the meter.  Measuring a cheap radio with an equally cheap meter could be an exercise in frustration. Do you have a friend with a more expensive wattmeter that can verify your results?  

 

[WRUA262]

33 minutes ago, Sshannon said:

It’s important to note that there have been a lot of Surecom SW-102 meters reported within this forum that have really lousy accuracy.  How can you be sure it’s not the meter.  Measuring a cheap radio with an equally cheap meter could be an exercise in frustration. Do you have a friend with a more expensive wattmeter that can verify your results?  

 

The Surecom measured the low setting at just over 5 watts, which is exactly where it should be. I have no reason to think that the meter isn't working correctly. Since it gave exactly the same reading into a dummy load as it did the antenna itself, I'd wager that the meter is not the problem.

But to answer your question, I don't know of anyone close to me at this point with a different meter to verify the results.

[Sshannon]

8 minutes ago, WRUA262 said:

The Surecom measured the low setting at just over 5 watts, which is exactly where it should be. I have no reason to think that the meter isn't working correctly. Since it gave exactly the same reading into a dummy load as it did the antenna itself, I'd wager that the meter is not the problem.

But to answer your question, I don't know of anyone close to me at this point with a different meter to verify the results.

All meter ranges are calibrated at two separate points with the expectation that everything in between is linear.  It’s very possible, perhaps even probable, that the low points would be quite close.  It’s also very possible (perhaps even probable) that the radio puts out less power than advertised.  It’s a dilemma, for sure.

[marcspaz]

3 hours ago, Sshannon said:

It’s important to note that there have been a lot of Surecom SW-102 meters reported within this forum that have really lousy accuracy.  How can you be sure it’s not the meter.  Measuring a cheap radio with an equally cheap meter could be an exercise in frustration. Do you have a friend with a more expensive wattmeter that can verify your results?  

 

 

^^^ This!   have mentioned this a dozen times if I mentioned it once.  The Surcom SW-102 is a user-adjustable tool that needs to be calibrated.  I have had to re-calibrate mine 3 times this year.  Even if it was accurate out of the box, that doesn't mean its still accurate. 

 

2 hours ago, WRUA262 said:

The Surecom measured the low setting at just over 5 watts, which is exactly where it should be. I have no reason to think that the meter isn't working correctly. ...

 

That doesn't really mean anything.  I'm not being a smart@$$ when I say the closer to zero you get, the more accurate the meter is. 

 

Also, I just did a test of my radio using a Surecom and shared the video.  The Surecom was out of calibration after I had calibrated it at the end of last summer.  It was misreading a 101w radio as 78w.  It also had a bad SWR reading on my dummy load (result of bad power reading).  I had to calibrate it with proper tools (or you can use known good meters to compare) so I could use the digital meter in the video, to provide accurate results.

 

The reality is, the fact that you get the same results on the antenna and the dummy load leads me to trust the results even less.

[WRUA262]

1 hour ago, marcspaz said:

 

^^^ This!   have mentioned this a dozen times if I mentioned it once.  The Surcom SW-102 is a user-adjustable tool that needs to be calibrated.  I have had to re-calibrate mine 3 times this year.  Even if it was accurate out of the box, that doesn't mean its still accurate. 

 

 

That doesn't really mean anything.  I'm not being a smart@$$ when I say the closer to zero you get, the more accurate the meter is. 

 

Also, I just did a test of my radio using a Surecom and shared the video.  The Surecom was out of calibration after I had calibrated it at the end of last summer.  It was misreading a 101w radio as 78w.  It also had a bad SWR reading on my dummy load (result of bad power reading).  I had to calibrate it with proper tools (or you can use known good meters to compare) so I could use the digital meter in the video, to provide accurate results.

 

The reality is, the fact that you get the same results on the antenna and the dummy load leads me to trust the results even less.

Not sure how to re-calibrate the Surecom. Is that as simple as resetting it or is there some other way to recalibrate it? There is certainly nothing on the chinglish instructions as far as dialing it in. I'll tell you this, I'm not going to spend a bunch more $ buying a more testing equipment that I might use once. If I was making money off it, sure, it would be worth the investment, but I'm not... so I won't.

[gortex2]

Why dont you just use your radio and dont worry about it ? Radios cost money to buy quality stuff. If you buy a CCR and CCR meter you get what you pay for. 

[marcspaz]

1 hour ago, WRUA262 said:

Not sure how to re-calibrate the Surecom. Is that as simple as resetting it or is there some other way to recalibrate it? There is certainly nothing on the chinglish instructions as far as dialing it in. I'll tell you this, I'm not going to spend a bunch more $ buying a more testing equipment that I might use once. If I was making money off it, sure, it would be worth the investment, but I'm not... so I won't.

 

 

When you go in the menu, there are options to calibrate the frequency display (0.1KHz increments) and the power measurements. They are VHF, UHF, low power VHF, low power UHF, adjustable in a plus/minus percentage of the base reading, up to 100%.

 

I can't help you on not wanting to spend money on a device to calibrate against. Everything that measures, requires calibration at one point. The cheaper the device, the less accurate and more often the issue of calibration occurs. 

 

My best advice is, buy a much more expensive, quality meter that is known to be accurate from the manufacturer and doesn't require calibration often (maybe after a few years or after a drop/impact/etc.), or don't worry about it and just use what you have as a binary device.  Have to warn you though, you're going to spend several hundreds of dollars ($400-$500+), but still won't completely get away from the need for calibration. 

[Sshannon]

It's also important to remember that the power output will have less effect than you might expect.  That's not to say it'll have no effect, otherwise we would all have 100 mw handhelds and be delighted, but the effect on range is certainly not proportional to power. Using the Free Space Path Loss calculator at Pasternak, the loss increases by 6 dB for every doubling of distance. If you're down to 15 watts, from 25 watts, you have lost 2.2 dB.

https://www.pasternack.com/t-calculator-fspl.aspx?utm_campaign=Power_Combiners&keyword=&gclid=CjwKCAiArY2fBhB9EiwAWqHK6m1sMnUKdXjKlSefQDa1mTL4ALA32Cg53fVUHsRkay7AEJN_aHBRqRoCsIAQAvD_BwE

[Radioguy7268]

Don't let science get in the way of advertising. More watts is always more better! Who needs a receiver? I got 45 watts out, a cigarette lighter plug and a mag mount!

[wayoverthere]

1 hour ago, Radioguy7268 said:

Don't let science get in the way of advertising. More watts is always more better! Who needs a receiver? I got 45 watts out, a cigarette lighter plug and a mag mount!

I'm holding out for one I can run off of one of the USB power adapters

[PartsMan]

I once did a range test with a friend.

We got about ten miles on medium with our mobile radios. About 10 watts.

When we cranked up to high, 20 and 25 watts, we gained about 100 yards.

After that my desire for a 50 watt radio diminished a lot.